Revenues (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 278	$ 255	$ 606	$ 536
Regulated Electric | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	243	224	493	448
Regulated Natural Gas | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	35	31	113	88
Retail
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	221	204	496	434
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	85	79	208	181
Retail | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	134	123	284	250
Retail | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2	4	3
Retail | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	188	174	387	349
Retail | Regulated Electric | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	67	64	148	135
Retail | Regulated Electric | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	119	108	235	211
Retail | Regulated Electric | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2	4	3
Retail | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	33	30	109	85
Retail | Regulated Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	18	15	60	46
Retail | Regulated Natural Gas | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	15	15	49	39
Retail | Regulated Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Interchange
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	52	46	99	92
Interchange | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	52	46	99	92
Interchange | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2	4	3
Other | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	1	2	1
Other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	1	2	2
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	275	252	599	529
Total revenue from contracts with customers | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	241	221	488	442
Total revenue from contracts with customers | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	34	31	111	87
Alternative revenue and other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	3	3	7	7
Alternative revenue and other | Regulated Electric
Disaggregation of Revenue [Line Items]
Alternative revenue and other	2	3	5	6
Alternative revenue and other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Alternative revenue and other	$ 1	$ 0	$ 2	$ 1